JPH088238B2 - Method for manufacturing semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method during a manufacturing process of a semiconductor device, and more particularly to a method of processing a semiconductor device containing tantalum as a constituent element.

2. Description of the Related Art In a semiconductor device formed on a Si substrate or a glass substrate, various processes have been considered by using a resist pattern as a mask when forming various patterns and utilizing etching selectivity in a multi-layer period. . In particular, tantalum oxide has been widely studied as an insulator having a high dielectric constant. TaN is used as a resistor, and TaSi ₂ and Ta are used as electrodes.

Further, from the viewpoint of the process, it can be used as an etching stopper because it is difficult for the solution to be etched by hydrofluoric acid-based etching that is widely used for Si-based etching. As integrated circuits have become finer in recent years, CF
Dry etching using an etching gas containing F such as ₄ , CHF ₃ , and SF ₆ has been used.

Problems to be Solved by the Invention However, the etching with such an etching gas has a drawback that tantalum oxide, TaSi, and Ta are etched, and the etching stopper does not function like wet etching. Sometimes, even glass substrates and silicon substrates were etched. That is, a processing method for finely processing a layer formed on tantalum oxide without using a tantalum or a tantalum compound as an etching stopper to damage the substrate was not a conventional method.

Means for Solving the Problems In the present invention, after a layer containing tantalum oxide as a main component is formed on a substrate, a first gas having fluorine as a constituent element and a second gas having nitrogen as a constituent element are provided. The layer formed on tantalum oxide is etched by using the contained etching gas, and the above problems can be solved by using this method.

The first gas containing fluorine as a constituent element is CF ₄ ,
CHF ₃ etc. fluorocarbon absorption gas, nitrogen fluoride such as NF ₃ , XeF
Etc. As the second gas, nitrogen oxides such as N ₂ and N ₂ O,
There are NH ₃ , NF _3, etc. Therefore, since nitrogen fluoride such as NF ₃ is contained in both the first and second gases of the present invention, the same gas such as nitrogen fluoride does not deviate from the spirit of the present invention. Also, an inert gas may be mixed.

As means for forming radicals or ions of fluorine or nitrogen in the above-mentioned first and second gases, means for exciting a substance such as plasma discharge and ultraviolet light irradiation may be generally used.

Action Fluorine radicals react with Si to form silicon fluoride, and tantalum becomes tantalum fluoride gas with high vapor pressure, which promotes etching. Here, in the presence of fluorine, the nitrogen radical does not react with Si and proceed to silicon nitride. However, it is considered that even in the presence of fluorine, the reaction of tantalum to the tantalum nitride having a low vapor pressure proceeds on the surface of tantalum and the tantalum is not further etched, so that a large etching selection ratio can be obtained.

Example (Example 1) TaOx12 of 1000 Å is formed on a hard glass 11 (Corning 7059) by a reactive sputtering method at a substrate temperature of 150 ° C in a target of Ta and Ar of 4 m Torr and O ₂ of 4 m Torr. Then I
After the TO is formed by the sputtering method, the ITO is pattern-etched with HI to form the ITO pattern 13. Next, SiH ₄ , PH ₃ and B ₂ H ₆ were introduced in appropriate amounts and plasma CVD was used to deposit aSi of Pin from the lower layer.
(Amorphous silicon) 14, 15 and 16 are formed by stacking. When this sample is placed in a chamber and irradiated with an ultraviolet laser 17 while flowing NF ₃ gas, only aSi is etched when irradiated. At this time, ITO17, T
aOx12 is hardly etched. After that, the solar cells can be formed by forming the electrodes.

(Example 2) SiO ₂ 22 is formed on a hard glass substrate 21 (Corning 7059) by an atmospheric pressure CVD method to 2000 Å. Next, Ta23 is formed by DC sputtering to 1000 liters. This second 3 CF ₄ by a chemical dry etching apparatus shown in FIG, 20 Pa, and etching with O ₂ 5 Pa, to form a gate pattern made of Ta 23. In FIG. 3, 31 is a sample substrate, 32 is a container (chamber), 100 is a microwave of 2.45 GHz, 101 is plasma, 102
Is a CF ₄ , O ₂ , N ₂ gas, and 103 is an exhaust part. Next, SiN (silicon nitride) 24 and aSi (amorphous silicon) 25 are continuously formed by the PCVD method. Sample 31 shown in Figure 3
When the two layers 24 and 25 are placed in 32 and chemical dry etching is performed with CF ₄ 20Pa, O ₂ 5Pa and N ₂ 5Pa, SiN24 and aSi25 are etched and patterned according to the mask pattern, but Ta23 and SiO ₂ 22 Is hardly etched. Si
In the remaining regions of N24 and aSi25, MoSi26 and Al27 are formed by DC sputtering method and patterned to form source and drain electrodes. In this way, the TFT is formed. The TFT array using this TFT manufacturing method is also useful as a liquid crystal display substrate.

Although the above-described examples show the case of photoexcitation and chemical dry etching, reactive ion etching or the like has the same effect.

Also, an example of a glass substrate is shown, but the same applies to a Si substrate or the like. Although an example of aSi is shown as the layer to be etched, single crystal silicon, polycrystalline silicon, SiNx,
The present invention can be applied to those that are etched by fluorine radicals such as SiO ₂ .

EFFECTS OF THE INVENTION As described above, according to the manufacturing method of the present invention, it is possible to finely etch a layer without damaging the base.

[Brief description of drawings]

1 is a process cross-sectional view of a solar cell using the manufacturing method of the present invention shown in Example 1, FIG. 2 is a process cross-sectional view of a thin film transistor using the manufacturing method of the present invention shown in Example 2, FIG. 3 is a schematic view of the chemical dry etching apparatus used in the second embodiment. 12 …… tantalum oxide, 23 …… tantalum, 31 …… sample substrate.

Claims (2)

[Claims] 1. A method for manufacturing a semiconductor device, comprising: forming a first layer containing tantalum as a constituent on a substrate; and etching at least one second layer formed on the first layer. And a step of etching the second layer using an etching gas containing a first gas having fluorine as a constituent element and a second gas having nitrogen as a constituent element. Manufacturing method of semiconductor device. 2. A method of manufacturing a semiconductor device, comprising forming a first layer containing tantalum as a constituent on a substrate and then etching at least one second layer formed on the first layer. And a step of etching the second layer using an etching gas containing a gas having fluorine and nitrogen as constituent elements.